Die set

ABSTRACT

A die set includes a die shoe with upstanding pins and a punch holder having a depending punch and bushings which reciprocally receive the pins of the die shoe with the center distance of the pins greater than the center distance between the bushings to cause line contact of a portion of the circumference of the pins with the bushings. This engagement of the pins and bushings minimizes tilting of the punch holder and facilitates removal of the punch holder and also allows greater deflection of the die shoe in use before the pins contact the walls of the bushings thus reducing wear and galling of the pins and bushings.

I Umted States Patent [1 1 3,776,086

Janiszewski Dec. 4, 1973 [54] DIE SET 2,751,260 6/1956 Janiszewski 83/637 x 76 I t Kas' anisze ski 5426 w. l men or gvz z Wis Primary Examiner-Andrew R. Juhasz 53219 Assistant Examiner-W. D. Bray AttorneyHenry C. Fuller, Jr. [22] Filed: July 21, 1972 [21] Appl. No.: 273,893 ABSTRACT A die set includes a die shoe with upstanding pins and [52] US CL 83/637 83/561 83/698 a punch holder having a depending punch and bush- 308/4 ings which reciprocally receive the pins of the die shoe [51] Int Cl. 526d 5/08 with the center distance of the pins greater than the [58] Fig. 637 center distance between the bushings to cause line 4 308/4 6 contact of a portion of the circumference of the pins with the bushings. This engagement of the pins and bushings minimizes tilting of the punch holder and fa- [56] U SZ:Z? :Z; cilitates removal of the punch holder and also allows N greater deflection of the die shoe in use before the et al. X pins ontact the walls of the bushings thus reducing wear and galling of the pins and bushings. 3:032:378 5/1962 5 Claims, 5 Drawing Figures I" i 4c 40 I 42 I I H| 4/ DIE SET BACKGROUND OF THE INVENTION A conventional die set has a pin center distance equal to the bushing center distance and the punch holder reciprocates on the pins of the die shoe on a film of grease which locates the pins in the centers of the bushings. When the movement of the punch holder stops and if the punch holder is supported only by the pins, the punch holder can tilt at an angle, with the bushings contacting the pins at the edges of the bushings, causing the punch holder to bind when the punch holder is removed from the die shoe. In addition, with a typical die set, the pressure caused by blanking, drawing, or forming causes a deflection in the die shoe caused by the deflection of the bolster spanning the hole in the press bed. This deflection causes the pins to cock inward and press against the bushing causing undue wear of the bushings and galling.

SUMMARY OF THE INVENTION In accordance with the invention, the spacing of the die shoe pins and the bushings in the punch holder is such that the periphery of the pins is in line contact with the bushing surfaces rather than centered in the bushings as with the prior art die sets. Thus, all the clearance is on the inside of the bushing. This construction minimizes tilting of the punch holder out of parallel with the die shoe and press bed to prevent binding of the pins on the housing, thus greatly facilitating separation of the punch holder from the die shoe. In addition, the unequal center to center distance of the bushings and pins with all the clearance on the inside of the bushings allows greater deflection of the die shoe before the pins contact the adjacent walls of the bushings,

thus minimizing wear and galling of the pins and bushings.

The die set of the invention also includes means for adjustably securing the bushings to the punch holder to facilitate rotation of the bushings after wear along the line contact surfaces.

Further objects, advantages and features of the invention will become apparent from the following disclosure.

DRAWINGS FIG. 1 is a side elevational view in fragmentary section of a prior art die set showing binding of the pins in the bushings.

FIG. 2 is a prior art view of a die set showing tilting of the punch holder and binding of the pins in the bushings during removal of the punch from the die shoe.

FIG. 3 is an enlarged fragmentary sectional view with parts broken away of a die set in accordance with the invention.

FIG. 4 is a reduced plan view of the die set shown in FIG. 3.

FIG. 5 is a view similar to FIG. 1 with a modified embodiment of the means for adjusting the pins in the bushings.

DETAILED DESCRIPTION Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. The scope of the invention is defined in the claims appended hereto.

FIG. 1 discloses a prior art set with a punch holder 10 having bushings 12 and 14 which receive pins 16 and 18 on a die shoe 20. The punch holder also carries a punch 22 engaged with a work piece 23. The die shoe 20 is shown in a condition of deflection wherein the shoe 20 is other than parallel with the punch holder 10 as a result of deflection of the bolster spanning the press bed (not shown) during use. The bushings and pins in the FIG. 1 prior art die set are spaced at an equal center to center distance which results in wear and galling at the points W. In FIG. 2, the punch holder 10 is cocked at an angle A out of parallel with the die shoe during removal of the punch from the die shoe causing the pins to bind at the points S of the bushings andinterfering with removal of the punch holder 10.

FIGS. 3 and 4 disclose a die set in accordance with the invention with pins 30 and 32 for a die shoe 34 having a distance D between the centers 36 and 38 of the pins greater than the distance Z between the centers 40 and 42 of the bushings 37, 39 to cause line contact of the periphery of the pins with the bushings at points 44 and 46. The preferred difference in distance of D with respect to Z is equal to the sum of the average clearance of the pins in the bushings. More specifically, if the maximum clearance between pin 30 and the wall portion 41 of the bushing 37 when the pin and bushing are in line contact at 44 is Y and the maximum clearance between pin 32 and bushing 39 when the pin and bushing are in line contact at 46 is X, then the center distance D between the pins 30 and 32 is equal to the sum of Z, Y/2, and X/2.

The line contact between the pins and the bushings prevents tilting and binding of the bushings with respect to the pins as shown in the prior art device in FIG. 2 facilitating easy removal of the punch holder from the die shoe. With prior art die sets, tilting can be reduced by having bushings of a greater length than is required with die sets of the invention.

The increase in clearance on the inside of the bushings with the pins afi'ords greater deflection of the die set during deflection of the die shoe as shown in FIG. 1 before the pins contact the adjacent walls of the bushings thus reducing wear and galling of the pins and bushings. 7 With the unequal centering of the pins and bushings in accordance with the invention, the wear results at the line contact points 44 and 46 and the bushings can be rotated once the wear occurs to provide new guiding bushing surfaces.

a In FIG. 3 means are disclosed for adjustably securing the bushing 37 in the punch holder 49 to afi'ord rotation of the bushing 37 after use to employ a new guiding bushing surface for the pin 30. As disclosed, the means includes a ring 51 having a flange 52 which is received in an annular groove 53 in the bushing. Bolts. 54.

arranged around the ring 5 1 and threaded into the punch holder 49 clamp the bushing to the punch holder 49.

Clamping arrangements can be employed to maintain the line contact of the pins and bushings. In FIG. 3 a clamp 56with a bolt 58 engages the pin 32 and a bolt 60 engages the bushing. The clamp 56 facilitates alignment of the pin 32 in the bushing 39 during assembly to cause the desired line contact. In FIG. 5 a bolt- 62 threaded into the bushing 39 provides adjustment of the pin 32 with respect to the bushing 39.

What is claimed is:

1. In a die set including a punch holder with spaced apertures in said punch holder, bushings in said aper tures and a die shoe with upstanding pins received in said apertures with clearance between said bushings and pins to enable relative movement between said die shoe and said punch holder, the improvement wherein the spacing between the axial centers of the apertures in said bushings is less than the distance between the axial centers of the pins, with said pins being in line contact along their circumference with said bushings.

2. The improvement of claim 1 wherein the difference between the center distance of the pins and the center distance of the bushings is equal to the average clearance of the pins in the bushings.

3. The improvement of claim 1 wherein the difference in radius between one of said pins and one of said bushings is Y and the difference in radius between the other of said pins and the other of said bushings is X and the distance between said bushing centers is Z, and the center distance D between the pins is equal to the sum of Z, Y/2, and X/2.

4. The improvement of claim 1 including means for adjustably securing said bushings in said punch holder.

5. The improvement of claim 4 wherein said means affords radially adjustment of said pins with respect to said bushings. 

1. In a die set including a punch holder with spaced apertures in said punch holder, bushings in said apertures and a die shoe with upstanding pins received in said apertures with clearance between said bushings and pins to enable relative movement between said die shoe and said punch holder, the improvement wherein the spacing between the axial centers of the apertures in Said bushings is less than the distance between the axial centers of the pins, with said pins being in line contact along their circumference with said bushings.
 2. The improvement of claim 1 wherein the difference between the center distance of the pins and the center distance of the bushings is equal to the average clearance of the pins in the bushings.
 3. The improvement of claim 1 wherein the difference in radius between one of said pins and one of said bushings is Y and the difference in radius between the other of said pins and the other of said bushings is X and the distance between said bushing centers is Z, and the center distance D between the pins is equal to the sum of Z, Y/2, and X/2.
 4. The improvement of claim 1 including means for adjustably securing said bushings in said punch holder.
 5. The improvement of claim 4 wherein said means affords radially adjustment of said pins with respect to said bushings. 